A hitherto known battery cell of the above type includes: a power generating element that is formed of cathode and anode sheets, each sheet having electrode active material layers on both sides, wound up with a separator interposed between the cathode and anode sheets; current collectors each having a body to which an electrode terminal that is drawn out to the outside is conductively connected and connection strips extending from the corresponding body along the outermost circumferential surface of the layered electrode portion; and clamps that each hold the connection strips of the current collector in pressure contact with the outermost circumferential surface of the layered electrode portion while the connection strips are held in contact with the outermost circumferential surface of the layered electrode portion (cf., Patent Document 1).
The power generating element is formed by being wound up into a cylindrical shape, and then pressed from opposite sides into an oblong shape, i.e., a flattened shape, thus provided with curved portions located at upper and lower ends and a linear flat portion located between the curved portions. Cathode and anode layered electrode portions are formed at opposite ends of the power generating element. The body of each current collector has a triangular shape in plan view, and arranged on the upper surface of the curved portion of the power generating element along the axial direction no that its large-width portion (bottom portion) is positioned above the layered electrode portion while its small-width portion (crown portion) faces the small-width portion of the body of the opposite current collector. The small-width portion of the body is held in conductive connection with an electrode terminal that is drawn out to the outside. The connection strips of each current collector extend from the large-width portion of the body along the flat portion of the power generating element, thus forming a comb shape. Each pair of the connection strips forms a reverse U-shape to define a space therebetween into which the layered electrode portion is inserted